This invention relates to multi-layer injection molding apparatus and more particularly to such apparatus having integral multi-layer melt transfer and dividing bushings extending from a rear melt distribution manifold through openings in a front melt distribution manifold to aligned heated nozzles.
Injection molding apparatus for making multi-layered protective containers for food or preforms or parisons for beverage bottles are well know. Often the inner and outer layers are made of a polyethylene terephthalate (PET) type material with one or more barrier layers made of a material such as ethylene vinyl alcohol copolymer (EVOH) or nylon. As seen in U.S. Pat. No. 5,094,603 to Gellert which issued Mar. 10, 1992, it is known to have a number of heated nozzles each having an annular melt channel extending around the central melt channel extending forwardly from a single melt distribution manifold. U.S. Pat. No. 5,094,603 also shows the melt flowing to the annular melt channel in the heated nozzle dividing in a single layer melt distribution plate mounted between the rear end of the heated nozzle and the front end of the melt distribution manifold.
However, when molding materials having different injection temperatures, it is preferable to distribute the two melts through front and rear melt distribution manifolds which are spaced apart. While apparatus having spaced melt distribution manifolds is shown in U.S. Pat. No. 5,223,275 to Gellert which issued Jun. 29, 1993, it has the disadvantage that only the spacer discs mounted between the front and rear melt distribution manifolds only have a single melt outlet.